Claudio, thanks for the answer. What's a combination of repeating tasks? I get very interested to know it.

One of my projects that has to deal with irregular tasks is making a study schedule. For instance, I've broke down a whole study process into 20 sessions, and plan to finish 3-4 sessions per week (normally one session a day, but maybe 2-3 sessions for day-off), then how can I make toodledo work for this situation?

I would say that the tasks are not "repeating" because each session is unique (you're not going to complete Session 1 on Monday and then do it again on Tuesday and Wednesday), and the tasks have to be completed in a particular order.

So, I would create tasks for each session, with due dates consistent with the time frame required to complete the entire project. You can use the "Add Multiple Tasks" function to add 20 tasks quickly (Session 1, Session 2, etc. ) and then edit the due date and start date, or perhaps use a Date Modifier: http://www.toodledo.com/info/help.php?sel=42.

Each day you have a Session to complete, and perhaps one or two overdue Sessions. (Or, you could create a "master task" with 20 subtasks, put the subtasks in a particular order, leave out Due Dates, and just do each subtask in the order listed.)

Would that work for you?

As for "combination of repeating tasks", I just meant that some patterns require more than one repeating task because they cannot be handled by one task. For example, you want to do something on Monday every week, but every other week you also want do it on Wednesday. This requires two repeating tasks, even though the actual task is the same in each case.

I think the approach would go for me, which is very practical. In fact, I never knew due date modifiers already exist, it's something I was really looking for, especially the "optional" modifier, thanks for telling me this! By the way, the due-after modifier seems to not work, after adding ">" before due date, how come it gets changed to no due date instantly?!

Might I suggest a service called hassle.me, which sends out mails at irregular intervalls to an email-adress you supply. You set the average number of days between each reminder-mail, and then hassle.me adds a random variance to that. If you use your toodledo-adress as the adress, and format the subject according to their syntax, it will end up in the correct folder, status etc when it comes to your toodledo-account